The present invention relates to a plastic screw cap with tamper-evident ring.
Caps of the above type are already known commercially and comprise a cylindrical cup which is internally threaded in order to be screwed onto the top of the container (bottle).
A so-called tamper-evident ring is coupled to the rim of the cup by means of breakable bridges and is internally provided with engagement elements constituted by flaps or by a collar which, when the cap is applied so as to close the container, engage under an annular raised retention portion of the container. By unscrewing the cap, the flaps or the collar abut against the annular raised portion and retain the ring, while the resulting axial traction force breaks the bridges.
Conventional caps entail the problem of ensuring that during application to the container the flaps or collar can widen or otherwise be elastically deformed in order to pass over the raised retention portion of the bottle and then close again below said raised portion, so as to allow the separation of the tamper-evident ring during the unscrewing of the cap and clearly indicate that the container has been opened.
However, in currently commercially available caps the tamper-evident ring, in order to ensure that the teeth or collar remain engaged below the annular raised portion of the container during unscrewing and can thus ensure the breaking of the bridges, has an excessively rigid structure and therefore passing over the raised portion when the cap is applied to the container is critical.